The present invention relates generally to mold forming apparatus and more specifically to the structure and arrangement of a pattern device useful in the formation of foundry molds. The pattern device of the invention is of the type which can be moved from a lifting station, where formed mold halves may be lifted from the pattern plates, to a pattern plate exchange station.
Pattern devices for utilization in the formation of foundry molds are known. Such pattern devices combine a frame structure, arranged as a pattern plate centering device, with pattern plates in order to form a unit and in order to connect the frame to a molding table. In order to perform an exchange of the pattern plates of these pattern devices, at least one lifting unit is provided at the molding table. The lifting unit lifts the pattern plates while in a loose state out of a frame to an extent sufficient to enable the pattern plates to be grasped laterally so that an exchange may be effected.
Since, in pattern devices of this type, due to the manner in which the devices are arranged, the pattern plates can be lifted only to a limited height, the molding sand which falls onto the molding table of the apparatus cannot be removed. As a result, this causes the pattern plates to be oriented in a higher position than is desired thereby preventing a satisfactory closing or joinder of the sand between the lower and upper parts of the apparatus.
A further disadvantage resides in the fact that the pattern plate exchange procedure will result in long plates arranged in a pattern plate carrier. The pattern plates are pressed with their stop faces against stop faces which are part of the pattern plate carrier. Such centering devices utilize a piston-cylinder unit used as a pressure transmitting means for vertical centering of a pattern plate. The centering device has a plate shaped cylindrical part which acts through intermediate plates on the pattern plate and which is provided with cylinder bores which are connected to each other through several transfer ducts. Arranged in these cylinder bores are piston bodies which are supported by the bottom of the pattern plate carrier. When connected to an energy source, the centering device presses the pattern plate with the stop face against the bolt heads of setbolts which are passed through the pattern plates, the intermediate plates and the cylinder parts and which are screwed into the bottom of the pattern plate carrier.
This centering device also has the disadvantage that the molding sand cannot be removed from inside of the cup shaped pattern carrier during pattern plate exchange without requiring disassembly not only of the pattern plates but additionally all other parts in the pattern carrier. Furthermore, the centering device had the disadvantage that, due to the piston-cylinder unit, the structural height as well as the weight are doubled considered in relationship to comparable pattern devices. A further disadvantage resides in the fact that precision setbolts must be screwed out and back during each pattern exchange. A still further disadvantage resides in the fact that bolt heads as well as dividing walls involved tend to reduce the utilization factor of the pattern surface with respect to the pattern lining. With regard to an example of prior art such as that discussed above, reference is made to German Offenlegungsschrift No. 1,808,493.
The present invention is directed to the task of eliminating the disadvantages of the prior art discussed above.